The Space Shuttle Atlantis arrived at its launch pad at NASA's Kennedy Space Center, Fla., at 8:54 a.m. EDT Wednesday on top of a giant vehicle known as the crawler transporter.

After two days of weather delays, the crawler transporter began carrying Atlantis out of Kennedy's Vehicle Assembly Building at 1:05 a.m. Wednesday. The crawler's maximum speed during the 4.2-mile journey reached 1 mph.

While at the pad, the shuttle will undergo final testing, payload installation and a "hot fire" test of auxiliary power units to ensure proper function. When testing is completed, the rotating service structure will be moved around the vehicle to protect it from the elements.

The launch window for the Atlantis mission to the International Space Station opens on Sunday, Aug. 27. The mission, designated STS-115, will be the first to perform a major expansion of the station since December 2002.